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MUNICH -- When different troponin assays disagreed on whether someone could be ruled out for acute coronary syndrome (ACS), patients ended up with the same outcomes regardless of the test that was used to guide treatment, according to a stepped-wedge, cluster-randomized controlled trial presented here.

Patients reclassified as positive for ACS with a high-sensitivity cardiac troponin I (hs-cTnI) assay, after a negative result on contemporary cardiac troponin I (cTnI) testing, were just as likely to suffer a subsequent MI or to die from cardiovascular causes within a year as those for whom diagnosis relied solely on cTnI (12% versus 15%, respectively, adjusted OR 1.10, 95% CI 0.75-1.61).

Only one-third of the 1,771 reclassified patients (out of 10,360 evaluated in the trial) actually turned out to have MI, however, whereas half had myocardial injury, reported Nicholas Mills, MD, PhD, of the University of Edinburgh, Scotland, at the European Society of Cardiology annual congress.

The results were published simultaneously in , where Mills and colleagues suggested that one take-away from the study is that the diagnostic threshold for MI with hs-cTnI — the 99th percentile from a normal reference population — may not be appropriate.

Rates of percutaneous coronary intervention did not go up significantly after hospitals implemented hs-cTnI testing (going from 3% to 5%), though more patients underwent coronary angiography (from 4% to 11%).

"It's reassuring for me that there was no excess of treatment," Mills said in a press conference.

Nevertheless, hospital stay was 30 hours longer among those who were reclassified on the basis of the hs-cTnI test.

Several factors may explain why a troponin test that's more accurate for ruling out ACS did not produce better outcomes.

"I'd say that the tools we have to improve outcomes are blunt and imperfect and on the margins are more effective in higher-risk populations identified by the traditional assays. That is, what we are capturing here is probably less amenable to benefit from medical or interventional therapies," speculated Ethan Weiss, MD, of University of California San Francisco, in an interview.

"The study shows that hs-troponin assay is very effective in identifying patients with myocardial injury but has very poor specificity for patient with MI," commented Sorin Brener, MD, of New York-Presbyterian Brooklyn Methodist Hospital in New York City. Neither Brener nor Weiss were involved with the trial.

Importantly, 83% of reclassified patients were women, in whom treatment effectiveness is uncertain, given a sex difference in disease mechanisms, Mills said.

For one, women tend to have more microvascular disease that a treatment aimed at MI can't address, noted Mariell Jessup, MD, the American Heart Association's incoming chief science and medical officer.

High-STEACS was conducted at ten Scottish hospitals where 48,282 consecutive patients (61 years old on average, 47% women) arrived at the emergency department with suspected ACS. Individuals were included in the study if they had both standard and high-sensitivity cTnI results available.

Outcome data were gathered from linked routine healthcare data available from the National Health Service and adjudicated by blinded cardiologists.

In this group, 17% of those with negative results on the contemporary assay got reclassified as having myocardial injury or infarction on the hs-cTnI assay.

Participating centers all started off concealing hs-cTnI results from the attending clinician such that the standard assay was used to guide care. Randomization led to five hospitals introducing hs-cTnI assay-based care after 6 months of this validation phase, and another five waiting to implement the new assay after 12 months (along with the sex-specific 99th percentile diagnostic threshold derived from a normal reference population, in line with the new 4th Universal Definition of Myocardial Infarction).

The first high-sensitivity troponin test was cleared by the FDA in 2017, but it remains seldom used in the U.S., Brener said.

This assay was labeled as “new-generation” by the FDA, not “high-sensitive,” noted Sanjay Kaul, MD, of Cedars-Sinai Medical Center in Los Angeles.

”The U.S. has been nearly a decade behind other countries in adopting hs-cTn assays in clinical practice,” he said. “In general, the adoption is lagging simply because of the challenges of implementing new protocols to optimize the clinical utility of this assay.”

The lower specificity of this technology “could potentially be a liability for cardiology consultants whose major focus is to rule-in MI and appropriately triage high-risk patients to more aggressive treatment interventions,” Kaul commented.

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